1. Field of the Invention
The invention in general relates to glass or glass ceramics. In particular, the invention relates to glass or glass-ceramics plates with a scratch-resistant layer.
2. Description of Related Art
Hard-material layers are used in many ways as coatings for components and tools in order to prolong the service life. Coatings on metals are used in such cases. Layers such as TiN or WC:C are deposited by means of an arc-supported method with process times of several hours. These methods are used with metal substrates in batch plants. The layers produced in these processes are frequently subjected to strong voltages, so that they often often crack in the plants. Crack-free, and particularly transparent, scratch-resistant layers on glass are especially difficult to produce with this technology.
Silicon nitride layers are in fact color-neutral and very transparent, but show transmission losses of approximately 7-10% absolute due to reflection losses, when compared with uncoated glasses having a transmission in the visible spectral region of approximately 92%. However, since highly transparent glasses are particularly required in the motor vehicle industry, any increase in transmission here increases the field of application of scratch-resistant coated plates.